Epigenetic Regulation of Estrogen Receptor Genes’ Expressions in Adipose Tissue in the Course of Obesity

Estrogen affects adipose tissue function. Therefore, this study aimed at assessing changes in the transcriptional activity of estrogen receptor (ER) α and β genes (ESR1 and ESR2, respectively) in the adipose tissues of obese individuals before and after weight loss and verifying whether epigenetic mechanisms were involved in this phenomenon. ESR1 and ESR2 mRNA and miRNA levels were evaluated using real-time PCR in visceral (VAT) and subcutaneous adipose tissue (SAT) of 78 obese (BMI > 40 kg/m(2)) and 31 normal-weight (BMI = 20–24.9 kg/m(2)) individuals and in 19 SAT samples from post-bariatric patients. ESR1 and ESR2 methylation status was studied using the methylation-sensitive digestion/real-time PCR method. Obesity was associated with a decrease in mRNA levels of both ERs in SAT (p < 0.0001) and ESR2 in VAT (p = 0.0001), while weight loss increased ESR transcription (p < 0.0001). Methylation levels of ESR1 and ESR2 promoters were unaffected. However, ESR1 mRNA in the AT of obese subjects correlated negatively with the expression of hsa-miR-18a-5p (r(s) = −0.444), hsa-miR-18b-5p (r(s) = −0.329), hsa-miR-22-3p (r(s) = −0.413), hsa-miR-100-5p (r(s) = −0.371), and hsa-miR-143-5p (r(s) = −0.289), while the expression of ESR2 in VAT correlated negatively with hsa-miR-576-5p (r(s) = −0.353) and in SAT with hsa-miR-495-3p (r(s) = −0.308). In conclusion, obesity-associated downregulation of ER mRNA levels in adipose tissue may result from miRNA interference.